Plasma CVD Methods

Using conventional thermal CVD various BN modifications but no c-BN or nano-cBN are formed. Therefore, to synthesize c-BN a plasma is applied to 

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Saitoh, H., et al., Synthesis of C-BN Film by Thermally Activated RF Plasma CVD Method, Japan New Diamond Forum, pp. 57-59, New Diamond (1988)... 

An HgCdTe layer 2, comprising photodiodes 3, is formed on a first side of a CdTe substrate 11. The detector is bonded to a silicon chip 7 by a flip-chip process. A reflection preventive film is formed on a second side, opposite to the first side, of the CdTe substrate. The film is formed by a cyclotron resonance plasma CVD method by introducing nitrogen, nitrous oxide and silane as reaction gas. The thickness of the film is selected so that the reflectivity is minimized for radiation having a wavelength to be detected by the photodiodes. 

An ECR-plasma CVD method is used to provide a protective film 27 on the mesas except for an exposed part of the pn-junction 26. ... 

A possible process for the SiOx film deposition at low temperatures below 70°C may be a special plasma CVD method which involves some elimination of carbonaceous compounds. In the plasma CVD, we believe that SiOx films are formed in two reactions (1) the bond scission of Si-OC bond in TEOS to form Si or SiO radicals, and (2) the recombination between two radicals to form Si-O-Si linkage. The repetitious combination of the two reactions leads to the Si-O-Si network, and as a result, a SiOx film is deposited. On the other hand, fragments eliminated from TEOS, ethyl or ethoxy radicals, also are recombined to form carbonaceous compounds and incorporated into the SiOx film. In the conventional plasma CVD process, the carbonaceous compounds in the deposited SiOx film are eliminated by the pyrolysis of the SiOx film at high temperature (500 ) (2). Therefore, in the SiOx-deposition on the PET film surface, some special process for the elimination of the carbonaceous compounds instead of the pyrolysis treatment should be investigated. 

Formation of a cBN film by the DC plasma CVD method has also been claimed (301). Laser-assisted plasma CVD, in which an excimer laser beam irradiated a growing film, was reported to be effective for growing cBN crystals (302,303). 

The various CVD processes comprise what is generally known as thermal CVD, which is the original process, laser and photo CVD, and more importantly plasma CVD, which has many advantages and has seen a rapid development in the last few years. The difference between these processes is the method of applying the energy required for the CVD reaction to take place. 

To deposit diamond by CVD, the carbon species must be activated since, at low pressure, graphite is thermodynamically stable and without activation only graphite would be formed. Activation is obtained by two energy-intensive methods high temperature and plasma. CVD processes based on these two methods are continuously expanded and improved and new ones are regularly proposed. 

In further sections extensions or adaptations of the PECVD method will be presented, such as VHF PECVD [16], the chemical annealing or layer-by-layer technique [17], and modulation of the RF excitation frequency [18]. The HWCVD method [19] (the plasmaless method) will be described and compared with the PECVD methods. The last deposition method that is treated is expanding thermal plasma CVD (ETP CVD) [20, 21]. Other methods of deposition, such as remote-plasma CVD, and in particular electron cyclotron resonance CVD (ECR CVD), are not treated here, as to date these methods are difficult to scale up for industrial purposes. Details of these methods can be found in, e.g., Luft and Tsuo [6]. 

Silicon microstructures can be categorized according to the dimensionality of the confinement. Most PL studies deal with silicon structures confined in three dimensions such dot-like structures are designated zero-dimensional (OD). An overview of size-dependent properties of silicon spheres is given in Table 6.1. Standard methods of generating such microstructures are gas-phase synthesis [Di3, Li7, Scl2], plasma CVD [Ru2, Col, Ta8] or conventional chemical synthesis [Mal5]. 

Summing up, it can be said that for the characterization of c-BN in unknown samples (mainly PVD and Plasma-CVD deposits), the results of only one analytical method are not sufficient for a definitive characterization. Measurements of the elemental composition in combination with IR and/or Raman and/or X-ray diffraction are necessary to ensure that c-BN is present. 

In contrast to plasma spraying, low pressure plasma CVD does not require any remote handling technique. However, there is yet no experience with large scale applications of this method, particularly in metallic vessels. This is the first goal towards which future studies have to be directed. Very little is also known about the adherence of the coatings deposited by low pressure plasma CVD and their resistance against thermal shock. The choice of the best material for such coatings is presently open to discussion. 

While plasma-enhanced methods are very usefiil to lower the substrate temperature, the as-deposited films are typically less conformal and often contain more surface impurities than competing methods. In this method, reactive radicals, ions, and atoms/molecules are formed in the gas phase that interact with the relatively low-temperature substrate to generate a film. Some of the more recent applications for plasma CVD include growth of cubic boron nitride (c-BN) thin films. 

Chemical vapor deposition (CVD) is an atomistic surface modification process where a thin solid coating is deposited on an underlying heated substrate via a chemical reaction from the vapor or gas phase. The occurrence of this chemical reaction is an essential characteristic of the CVD method. The chemical reaction is generally activated thermally by resistance heat, RF, plasma and laser. Furthermore, the effects of the process variables such as temperature, pressure, flow rates, and input concentrations on these reactions must be understood. With proper selection of process parameters, the coating structure/properties such as hardness, toughness, elastic modulus, adhesion, thermal shock resistance and corrosion, wear and oxidation resistance can be controlled or tailored for a variety of applications. The optimum experimental parameters and the level to which... 

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